Method of making electrolytic devices



Dec. 10, 1946. .1. B. BRENNAN- METHOD OF MAKING ELECTROLYTIC DEVICESOriginal Filed Aug. 9, 1937 fA/VENTOE.

Fatenteci Eco. 10, 1946 METHOD OF MAKING ELECTROLYTIC DEVICES Joseph B.Brennan, Euclid, Ohio Original application August 9, 1937, Serial No.158,105. Divided and this application October 1, 1941, Serial No. 413,1?

(ill. 175-315) 3 Claims. i:

This invention relates to methods of making electrolytic devices andmore particularly to methods of making electrodes for electrolyticdevices such as electrolytic condensers, rectifiers, lightning arrestersand the like. This application is a division of my copending applicationSerial No. 158,105, filed August 9, 1937, now Patent No. 2,288,789. Inthis application the invention is described particularly with referenceto electrolytic condensers, but it is to be understood that theinvention may be applied to various other types of electrolytic devices.

It is among the general objects of my invention to provide an economicaland eflicient method of making electrodes for electrolytic devices suchas electrolytic condensers, and the like, which will operate eficientlyover long periods of time with low resistance and power factor losses.it is also among the objects of my invention to provide a method ofmaking electrodes for electrolytic devices which will have an effectivearea in contact with the electrolyte many times the plane area thereofand which, when provided with dielectric films and incorporated inelectrolytic condensers, will have capacities many times greater thancapacities of plane surfaced electrodes of similar size. Another objectis to provide a method of making an electrode comprising a strip havinga porous or permeable surface, the strip being flexible so that it canbe bent into various forms.

Briefly, I obtain the advantages noted above and economically produceefllcient electrodes for electrolytic devices by spraying molten metalsuch as finely divided aluminum of high purity upon a base whichpreferably consists of a thin, flexible strip of porous or wovenmaterial. As described in my Patent No. 2,104,018 the sprayed depositconsists of a very large number of minute metallic particles whichadhere to the base and cohere to each other to produce a thin porouslayer that is conductive throughout substantially its entire area. Sucha layer deposited on a base which is also porous or permeable producesan electrode which is porous or reticulated throughout so that in usethe surface area of the metallic particles exposed directly to theelectrolyte is very large, resulting in a compact electrode which, whenprovided with a dielectric film, has a high capacity per unit or planearea. Furthermore, because of the very large area of metallic particlesin contact with the electrolyte and because of the porous structure ofthe electrode, the current densities may be kept at a low value, resistance is reduced and long life and efficient operation ofelectrolytic devices embodying my invention is thus insured.

Various metals may be deposited on suitable bases, depending upon theservice for which the electrode is intended. For example, in theproduction of filmed electrodes for electrolytic condensers, Ipreferably spray finely divided molten particles of high purity aluminumon strips of flexible porous material. The spraying operation may becarried out with well known apparatus in the manner described in greaterdetail in my patent aforesaid to produce a thin, porous or permeabledeposit of finely divided aluminum particles which adhere to the basematerial and cohere to each other to produce a layer which is conductivethroughout substantially its entire area, and which has a very largeeffective area. Various porous or woven materials may be usedadvantageously. For example, I may spray aluminum on a woven screencomposed of fine aluminum wires, upon a soft permeable base made ofpaper such as ordinary filter paper, upon cloth woven of textilematerials such as the gauze used in the manufacture of spacers forelectrolytic condensers, or upon cloth Woven of glass threads orfilaments.

The molten metallic particles are preferably sprayed on both sides ofthe base, a fine spray being employed. Preferably thin layers aredeposited in order to save material, it only being necessary to spray asufiicient thickness to insure that the sprayed layers will beconductive throughout substantially their entire areas. In the case ofaluminum anodes, for example, excellent results may be obtained byspraying layers about 1 to 3 thousandths of an inch thick. While thesprayed material does have the effect of stiflening the base material tosome extent, the completed electrodes retain suificient flexibility sothat they can be readily bent into desired shapes. When such electrodes,suitably provided with dielectric films, are incorporated inelectrolytic condensers, capacities as much as ten or more times thecapacity of condensers embodying ordinary aluminum electrodes of thesame plane area may be obtained. Furthermore, by the use of suchelectrodes condensers-having extremely low resistance and in which thepower factor losses are less than 4- per cent may be produced.

In spraying the metal on flexible porous strips of the types mentionedabove, I preferably carry out the operation in a continuous manner, thusproducing continuous strips of material suitable for use as electrodes.If the electrodes are intended for use as anodes in electrolyticcondensers, the sprayed strips may conveniently be formed with adielectric film by continuously passing them through a suitable film fogbath and applying the necessary voltages to the strips. Thereafter thestrips may be out into pieces of the desired length, bent into theproper shape if necessary. and incorporated in condensers.

Further advantageous features and other ob- -jects of my invention will,be evident to those skilled in the art from the following descriptionof preferred forms thereof, reference being made to the accompanyingdrawing in which Figure l is a plan view of an electrode made accordingto my invention; Figure 2 is a section through the electrode of Figure las indicated by the line 2-2; Figure 3 is a view of a paste typeelectrolytic condenser made according to my invention; Figure l is asectional view of a wet type electrolytic condenser made according to myinvention; Figure 5 is a section as indicated by the line 5-6 on Figure4; and Figures 6, '7 and 8 illustrate difierent steps in a. preferredform of my method.

As illustrated somewhat diagrammatically in Figures 1 and 2, the base orbacking material of an electrode made according to my inventionpreferably comprises a porous flexible strip i0 illustrated herein asbeing of woven material. Any suitable strands 0r filaments may beemployed in weaving the strip, it only being necessary to selectfilaments which will not react with or contaminate the electrolyte to beemployed in the condenser or other electrolytic device and which willnot otherwise adversely affect the operation of the device. Inconnection with electrolytic condensers, I prefer that the cloth bewoven or materials such as purified cotton threads or yarns, spun glassfilaments or fine metallic wires, the wires employed being of the samematerial as the metal to be sprayed thereon.

One or more thicknesses of material may be employed depending on thedesired thickness of the electrode which is to be produced. Whenmultiple layers of cloth are employed, the sprayed metal bonds thelayers together. The spraying of such thickness of metal, particularlywhen a gauze base is employed, results in an electrode that issufilciently open mesh and porous to permit light to pass through theelectrode layer at a multiplicity of points distributed throughout itsarea.

The strip 10 is provided with areas of sprayed metal IE on either sidethereof. Preferably the sprayed metal is only 0.001 inch to 0.003 inchin thickness, the thickness of the layers being greatly exaggeratedthroughout the drawing. The sprayed areas may be stopped short of theedges of the strip, particularly when a non-conductive material such ascotton cloth or glass cloth is employed, so as to provide insulatingedges for the electrodes. The layers I5 as previously noted comprise avery large number of finely divided cohering metallic particles, thelayers being conductive throughout substantially their entire area.

in an electrolytic condenser, the layers i 5 are formed of aluminum orother film forming metal, and after the spraying operation has beencompleted the electrodes may be provided with dielectric films bysubjecting them to electrolysis in a film forming bath such as asolution of borax and boric acid. The composition of the bath, thetemperature of the bath and the voltage applied to the electrodes allmay be controlled in ways well known to those skilled in the art anddepending upon the particular service for wh ch If the electrode isintended for use as an anode the electrode is intended. Various methodsof forming dielectric films are well known in the art. Such methods, perse, form no part of the present invention and therefore will not bediscussed further herein. For the purposes of this application, it issufiicient to state that the dielectric film conforms substantially. tothe contour of the many minute particles and thus the area of the filmis greatly increased as compared to the plane area of the electrode.

When such an electrode is incorporated in an electrolytic cell, theelectrolyte permeates the sprayed metallic layers as well as the porousbase material. Thus the eilective area of the electrade will be manytimes the plane area thereof. It will be evident that condensersembodying such electrodes will have very large capacities per unit ofplane area, since the capacity of a condenser is a function of the areaof the plates and in my device the area of the plate consists in the sumof the exposed areas of all of the many minute cohering metallicparticles.

Electrodes made according to my invention may be incorporated in varioustypes of electrolytic devices. In Figure 3, for example, I haveillustrated a paste type condenser embodying my electrodes. Asillustrated in the drawings, such a condenser, when intended for use indirect current circuits, may comprise a plurality of anodes as which maybe made in the manner described above, and a plurality of cathodes ii.The cathodes may be similar to the anode plates except that in the caseof condensers intended for direct current service, the cathodes need notbe provided with dielectric films. Or, if desired, the cathodes may bemade of ordinary metallic sheets or may be made of sprayed metals whichwill not become filmed such as copper. In condensers intended foralternating current service, both sets of electrodes are preferablyprovided with dielectric films. The anodes and cathodes are providedwith suitable terminals such as strips of metallic foil l8 and i9,respectively, and the electrodes may be prevented from coming in contactwith each other by suitable porous separators such as the paper strips20. The whole condenser assembly may be suitably impregnated with apasty or viscous electrolyte such as that described in my Patent No.2,095,966, issued October 19, 1937, and may be enclosed in a suitablecontainer or casing in a manner known to those skilled in the art.

As illustrated in Figures 4 and 5, electrodes made according to myinvention may be conveniently incorporated in electrolytic condensers ofthe wet or liquid type. Such a condenser may comprise a can 25 whichserves as the cathode of the condenser and also as a container for theelectrolyte. The can has a depending hollow neck portion 26 and isprovided with a closure member 21. The electrode 28 which constitutesthe anode of the condenser may be suitably supported within thecontainer and is immersed in the electrolyte'.

Preferably the anode 28 is constructed as illustrated in Figure 6 of thedrawing in such a manner as to eliminate the need for any mechanicalsupport for the anode within the container and also to eliminate thenecessity for providing a separate insulating spacer between the anodeand the container. Thus, the anode 28 preferably comprises a backing ofwoven nonconductive material 29 such as cotton or glass cloth havingsprayed areas 30 on either side thereof. The sprayed areas are spacedfrom the top and bottom edges of the strip 29 leaving unsprayednon-conductive areas 3| and 32, and there is a considerably unsprayedarea 33 at one 'end of the electrode. This electrode can very readily beincorporated in a condenser of the type illustrated in Figures 4 and 5by merely coiling the flexible electrode into the form of a spiral withthe unsprayed portion 33 forming the outer end of the spiral. Theportion 33 is of sufficient length to extend at least once around thespiral electrode to thus provide an insulating spacer integral with theelectrode and surrounding the sprayed areas 30. The spiral electrode isinserted into the can or container with the unsprayed area 33 inengagement with the inside of the can and the unsprayed lower edgeportion 3| in engagement with the bottom portion 34 of the can, theupper unsprayed edge 32 holding the electrode against upward movement byengaging, for example, the inwardly deformed portion 35 of thecontainer.

By this construction, the metallic sprayed areas of the electrode aresecurely and definitely spaced away from the container and closuremember by the non-conductive edge portions of the backing member 29 andthe entire electrode is mechanically supported within the container sothat no further mechanical support is necessary. Thus the usual rod orriser may be eliminated and the electrical contact between an exteriorcircuit and the electrode may be made by a lead-in, shown herein as awire 36, which extends downwardly through the neck portion 26.Preferably the lead-in 36 extends through a rubber gromet member 31, andthe neck portion is deformed inwardly as at 38 to compress the rubbergromet member and seal the neck portion and lead-in wire 36 againstleakage of fluid.

To provide an eflective and economical connection between the lead-in 36and the sprayed areas of the electrode, the lead-in is preferablyextended along the backing material as indicated at 39 in Figure 6. Thewire or other conductor may be secured to the backing material bystitching or may be merely laid along the strip before the sprayingoperation takes place. By this sequence of operation, efiective contactbetween the conductor and the sprayed material is assured, and thesprayed material secures the conductor to the base strip. Electrodes ofthis type, that is with an additional conducting member incorporatedtherein, may obviously be advantageously used in connection with the drytype of condenser hereofore described. Such electrodes have extremelylow resistance because of the fact that the conducting members extendthroughout the length of the electrode.

In Figures '7 and 8, I have illustrated steps of a method which may beconveniently employed in the manufacture of electrodes of the generaltype illustrated in Figure 6. As shown in Figure 7, the first steppreferably is to provide the strip of woven backing material 29 with aconducting member such as the stitched wires 39 extending throughout thelength of the strip which may be many feet long. At regular intervalsthroughout the strip, the wire or wires 39 are pulled out to form theloops 36 which ultimately constitute the terminal members for theelectrode. The spacing of the loops 36 is determined by the size of theelectrodes to be produced. The strip 29 with the stitching 39 therein isthen provided with the sprayed areas 30 as indicated in Figure 8. Thespraying operation may be carried out continuously, the strip beingsprayed simultaneously from both sides. Metallic shield members may beemployed to prevent the molten metal from adhering to the portions 3i,32 and 33, or, if desired, to cause the sprayed material to be depositedin any desired patterns.

The spraying operation thus produces a strip of backing material havinspaced sprayed areas thereon, the entire strip being conductivethroughout its length by reason of the conductors 39. The conductivestrip may then be passed through a forming bath in a continuous mannerso that as each portion of the strip leaves the bath it will be properlyformed with a dielectric film. Thereafter the strip may be cut in thespaces between the successive sprayed areas and the wire stitchingripped out from such spaces to provide the electrode illustrated inFigure 6. This electrode is then bent into a spiral or other convenientshape and may be incorporated into a condenser as described above.

Various changes and modifications in my invention will be evident tothose skilled in the art. Obviously my invention may be applied tovarious types of electrolytic devices and various changes can be made asto both the articles and methods disclosed herein without departing fromthe spirit and scope of my invention. It is therefore to be understoodthat my patent is not limited to the preferred forms of my inventiondisclosed herein or in any manner other than by the scope of theappended claims when given the range of equivalents to which my patentmay be entitled.

I claim:

1. A method of making flexible sheet electrodes for electrolyticcondensers which comprises spraying an open mesh cloth base with finelydivided particles of molten film forming metal and carrying out thespraying operation in such manner as to produce a conductive layer ofcohering metal particles adhering to said base, the layer being of suchthinness and the electrode bein sufficiently open mesh and porous topermit light to pass through the electrode layer at a multiplicity ofdistributed points throughout its area.

2. A method of making electrodes for electrolytic condensers whichcomprises stitching a wire along. a strip of backing material, pullingout loops of said wire at intervals along said strip, said loopsextending beyond an edge of said strip, spray depositing finely dividedparticles of molten metal on said strip and the portion of said wireoverlying said strip and cutting said strip into lengths suitable toform electrodes, each such length having associated therewith a portionof said wire projecting beyond the edge of said strip to constitute aterminal for such length.

3. A method of making electrodes for electrolytic condensers whichcomprises positioning a conductor along a strip of backing material,extending portions of said conductor beyond an edge or said strip atintervals along said strip, spray depositing finely divided particles ofmolten metal on said strip and the portion of said conductor overlyingsaid strip and cutting said Strip into lengths suitable to formelectrodes, each such length having associated therewith a portion ofsaid conductor projecting beyond the edge 01' said strip to constitute aterminal for such l n hs.

JOSEPH B. BRENNAN.

